Sulfur containing organosilicon compounds are useful as reactive coupling agents between rubber which contains carbon-to-carbon unsaturation and synthetic silica fillers (e.g. precipitated silica) providing for improved physical properties.
U.S. Pat. Nos. 6,096,832 and 6,184,306 disclose functionalized siloxy compounds for use in silica-filled rubber compositions as being represented by the general formula (I):
where R1, R2 and R3 are independently selected from the group consisting of alkoxy radicals having from 1 to 8 carbon atoms; R4 is selected from the group consisting of alkylene groups having from 1 to 15 carbon atoms and arylene and alkyl substituted arylene groups having from 6 to 10 carbon atoms; and n is an integer of from 1 to 8.
Functionalized siloxy compounds for use in silica filled rubber are also mentioned in U.S. Pat. No. 4,820,751.
Representative of various functionalized siloxy compounds may be, for example, siloxy compounds containing benzothiazole or thiocarbamyl moieties.
As used herein, the term or phrase “rubber or elastomer containing olefinic unsaturation” is intended to include both natural rubber and its various raw and reclaim forms as well as various synthetic rubbers. As used herein, the terms “rubber” and “elastomer” may be used interchangeably, unless otherwise prescribed. The terms “rubber composition”, “compounded rubber” and “rubber compound” may be used herein interchangeably to refer to rubber which has been blended or mixed with various ingredients and materials and such terms are well known to those having skill in the rubber mixing or rubber compounding art.
The term “phr” as used herein, and according to conventional practice, refers to “parts by weight of a respective material per 100 parts by weight of rubber, or elastomer.”